U.S. patent number 10,523,375 [Application Number 15/688,912] was granted by the patent office on 2019-12-31 for scheduling acknowledgements to received sub-frames in a multi-sim user equipment using a shared transmit chain when receiving data continuously on each sim.
This patent grant is currently assigned to Intel Corporation. The grantee listed for this patent is Intel Corporation. Invention is credited to Rishav Dev, Avinash K Dubey, Mohit Vajpeyee.
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United States Patent |
10,523,375 |
Dev , et al. |
December 31, 2019 |
Scheduling acknowledgements to received sub-frames in a multi-sim
user equipment using a shared transmit chain when receiving data
continuously on each sim
Abstract
A multi-SIM wireless device checks whether each of the (e.g.,
two) SIMs has received sub-frames in successive intervals prior to
a current interval. If such a condition is satisfied by all the
SIMs, the wireless device allocates several successive (transmit)
intervals to a first SIM before allocating next successive
(transmit) intervals to another SIM. If such a condition is not
satisfied, the sub-intervals may be allocated according to any
other approach (i.e., not constrained by the requirement of
successive sets of transmit intervals to the two SIMs) as suited
for the specific situation. The allocated sub-frame intervals are
used to send the acknowledgements of the previously received
sub-frames.
Inventors: |
Dev; Rishav (Bangalore,
IN), Vajpeyee; Mohit (Bangalore, IN),
Dubey; Avinash K (Bangalore, IN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Intel Corporation |
Santa Clara |
CA |
US |
|
|
Assignee: |
Intel Corporation (Santa Clara,
CA)
|
Family
ID: |
61758502 |
Appl.
No.: |
15/688,912 |
Filed: |
August 29, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20180097585 A1 |
Apr 5, 2018 |
|
Foreign Application Priority Data
|
|
|
|
|
Sep 30, 2016 [IN] |
|
|
201641033553 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W
72/1268 (20130101); H04W 72/02 (20130101); H04L
1/1822 (20130101); H04L 1/1854 (20130101); H04W
72/14 (20130101) |
Current International
Class: |
H04W
72/00 (20090101); H04W 72/02 (20090101); H04W
72/12 (20090101); H04L 1/18 (20060101); H04W
72/14 (20090101) |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Fang; Pakee
Attorney, Agent or Firm: Viering, Jentschura & Partner
MBB
Claims
We claim:
1. A wireless device comprising: a transmit chain; a first holder
for housing a first subscriber identity module (SIM); a second
holder for housing a second SIM; and one or more processors
configured to: receive concurrently or simultaneously a first
sequence of sub-frames for the first SIM and a second sequence of
sub-frames for the second SIM; determine whether the first sequence
of sub-frames and the second sequence of sub-frames are received in
respective successive sub-frame intervals prior to a current
interval; if the first sequence of sub-frames and the second
sequence of sub-frames are received in successive sub-frame
intervals prior to the current interval: allocate a first sequence
of successive sub-frame intervals to the first SIM to transmit
using the transmit chain; allocate a second sequence of successive
sub-frame intervals to the second SIM to transmit using the
transmit chain; transmit a first sequence of acknowledgements for
the first SIM in the first sequence of successive sub-frame
intervals, wherein each of the first sequence of acknowledgements
corresponds to a respective sub-frame of the first sequence of
sub-frames; transmit a second sequence of acknowledgements for the
second SIM in the second sequence of successive sub-frame
intervals, wherein each of the second sequence of acknowledgements
corresponds to a respective sub-frame of the second sequence of
sub-frames; and wherein the second sequence of acknowledgements are
transmitted after the first sequence of acknowledgements.
2. The wireless device of claim 1, wherein the determination is
performed again at a last sub-frame interval of the second sequence
of successive sub-frame intervals with the last sub-frame interval
as the current interval, wherein the allocation and the
transmission are repeated if the sub-frames of each of the first
sequence of sub-frames and the second sequence of sub-frames are
received in successive sub-frame intervals prior to the current
interval.
3. The wireless device of claim 2, wherein the first sequence of
sub-frames and the second sequence of sub-frames are received from
a base station, wherein the sub-frames in each of the first
sequence of sub-frames and second sequence of sub-frames are
transmitted by a respective one of a total of N1 number of
processes operational in the base station, wherein each of the N1
number of processes, after transmitting a corresponding sub-frame,
is to enter an inactive state until an acknowledgment to the
corresponding sub-frame is received from the wireless device.
4. The wireless device of claim 3, wherein the one or more
processers are further configured to determine a maximum number
(N2) of transmit opportunities provided to a wireless device for
acknowledging a respective sub-frame, wherein a duration of each of
the first sequence of successive sub-frame intervals and the second
sequence of sub-frame intervals is determined based on the lesser
of the values of maximum number of transmit opportunities N2
corresponding to the first SIM and the second SIM.
5. A method performed in a wireless device containing a first
subscriber identity module (SIM) and a second SIM, the first SIM
and the second SIM of the plurality of SIMs sharing a transmit
chain in the wireless device, the method comprising: receiving
concurrently a first sequence of sub-frames for the first SIM and a
second sequence of sub-frames for the second SIM; determining
whether the first sequence of sub-frames and the second sequence of
sub-frames are received in respective successive sub-frame
intervals prior to a current interval; and if the first sequence of
sub-frames and the second sequence of sub-frames are received in
successive sub-frame intervals prior to the current interval:
allocating a first sequence of successive sub-frame intervals to
the first SIM to transmit using the transmit chain; allocating a
second sequence of successive sub-frame intervals to the second SIM
to transmit using the transmit chain; transmitting a first sequence
of acknowledgements for the first SIM in the first sequence of
successive sub-frame intervals, wherein each of the first sequence
of acknowledgements corresponds to a respective sub-frame of the
first sequence of sub-frames; transmitting a second sequence of
acknowledgements for the second SIM in the second sequence of
successive sub-frame intervals, wherein each of the second sequence
of acknowledgements corresponds to a respective sub-frame of the
second sequence of sub-frames; and wherein the second sequence of
acknowledgements are transmitted after the first sequence of
acknowledgements.
6. The method of claim 5, wherein the determining is performed
again at a last sub-frame interval of the second sequence of
successive sub-frame intervals with the last sub-frame interval as
the current interval, wherein the allocation and the transmission
are repeated if the sub-frames of each of the first sequence of
sub-frames and the second sequence of sub-frames are received in
successive sub-frame intervals prior to the current interval.
7. The method of claim 6, wherein the first sequence of sub-frames
and the second sequence of sub-frames are received from a base
station, wherein the sub-frames in each of the first sequence of
sub-frames and second sequence of sub-frames are transmitted by a
respective one of a total of N1 number of processes operational in
the base station, wherein each of the N1 number of processes, after
transmitting a corresponding sub-frame, is to enter an inactive
state until an acknowledgment to the corresponding sub-frame is
received from the wireless device.
8. The method of claim 7, further comprising: determining a maximum
number (N2) of transmit opportunities provided to a wireless device
for acknowledging a respective sub-frame, wherein a duration of
each of the first sequence of successive sub-frame intervals and
the second sequence of sub-frame intervals is determined based on
the lesser of the values of maximum number of transmit
opportunities N2 corresponding to the first SIM and the second
SIM.
9. The method of claim 8, wherein at least N3 number of sub-frame
intervals are required to switch the transmit chain from one of the
first SIM and the second SIM to the other.
10. The method of claim 9, wherein a duration of each of the first
sequence of successive sub-frame intervals and the second sequence
of sub-frame intervals represents a transmission window size (TWS),
the method further comprising: pre-computing throughput loss values
for each combination of a set of TWS values and a set of values of
the maximum number N2; and for a specified value of N2, selecting
each of the first sequence of successive sub-frame intervals and
the second sequence of sub-frame intervals to equal that value of
TWS which is the greatest TWS value that results in zero throughput
loss.
11. The method of claim 10, wherein the wireless device is designed
to operate according to LTE (Long Term Evolution) specifications
for each of the first SIM and the second SIM, wherein the N1 equals
8 and the N3 equals 1 millisecond.
12. The method of claim 5, if both of the first sequence of
sub-frames and the second sequence of sub-frames have not been
received in successive sub-frame intervals prior to the current
interval, the acknowledgement for each of the first sequence of
sub-frames and the second sequence of sub-frames is sought to be
sent at a fourth number (N4) of sub-frames after receipt of the
corresponding sub-frame consistently.
13. A non-transitory machine readable medium storing one or more
sequences of instructions for operating a wireless device
containing a plurality of subscriber identity modules (SIMs), each
SIM having a corresponding receiver of a plurality of receivers, a
first SIM and a second SIM of the plurality of SIMs sharing a
transmit chain in the wireless device, wherein execution of the one
or more instructions by one or more processors contained in the
wireless device enables the wireless device to perform the actions
of: receiving concurrently a first sequence of sub-frames for the
first SIM and a second sequence of sub-frames for the second SIM;
determining whether the first sequence of sub-frames and the second
sequence of sub-frames are received in respective successive
sub-frame intervals prior to a current interval; and if the first
sequence of sub-frames and the second sequence of sub-frames are
received in successive sub-frame intervals prior to the current
interval: allocating a first sequence of successive sub-frame
intervals to the first SIM to transmit using the transmit chain;
allocating a second sequence of successive sub-frame intervals to
the second SIM to transmit using the transmit chain; transmitting a
first sequence of acknowledgements using the first SIM in the first
sequence of successive sub-frame intervals, wherein each of the
first sequence of acknowledgements corresponds to a respective
sub-frame of the first sequence of sub-frames; transmitting a
second sequence of acknowledgements using the second SIM in the
second sequence of successive sub-frame intervals, wherein each of
the second sequence of acknowledgements corresponds to a respective
sub-frame of the second sequence of sub-frames; and wherein the
second sequence of acknowledgements are transmitted after the first
sequence of acknowledgements.
14. The non-transitory machine readable medium of claim 13, wherein
the determining is performed again at a last sub-frame interval of
the second sequence of successive sub-frame intervals with the last
sub-frame interval as the current interval, wherein the allocation
and the transmission are repeated if the sub-frames of each of the
first sequence of sub-frames and the second sequence of sub-frames
are received in successive sub-frame intervals prior to the current
interval.
15. The non-transitory machine readable medium of claim 14, wherein
the first sequence of sub-frames and the second sequence of
sub-frames are received from a base station, wherein the sub-frames
in each of the first sequence of sub-frames and second sequence of
sub-frames are transmitted by a respective one of a total of N1
number of processes operational in the base station, wherein each
of the N1 number of processes, after transmitting a corresponding
sub-frame, is to enter an inactive state until an acknowledgment to
the corresponding sub-frame is received from the wireless
device.
16. The non-transitory machine readable medium of claim 15, wherein
the base station specifies a maximum number (N2) of transmit
opportunities provided to a wireless device for acknowledging a
respective sub-frame, wherein a duration of each of the first
sequence of successive sub-frame intervals and the second sequence
of sub-frame intervals is determined based on the lesser of the
values of N2 corresponding to the first SIM and the second SIM.
17. The non-transitory machine readable medium of claim 16, wherein
at least N3 number of sub-frame intervals are required to switch
the transmit chain from one of the first SIM and the second SIM to
the other.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to Indian Patent Application
Serial No. 201641033553, which was filed Sep. 30, 2016, and is
incorporated herein by reference in its entirety.
BACKGROUND
Technical Field
Aspects of the present disclosure relate generally to user
equipment used in wireless telephone networks, and more
specifically to scheduling acknowledgements to received sub-frames
in multi-SIM user equipment using a shared transmit chain when
receiving data continuously on each SIM (Subscriber Identity
Module).
Related Art
Wireless user equipment (UE), or wireless devices in general, refer
to instruments such as mobile phones using which users connect with
mobile telephone networks on a wireless medium, as is well known in
the relevant arts. In a common scenario, a UE interfaces with a
base station of a mobile telephone network providing the
corresponding user the facility of voice and data based
services.
UEs are often provided with multiple SIMs and associated receive
circuitry such that each SIM can receive data concurrently with any
other SIM. Each of such SIMs may also receive data continuously,
for example, when corresponding video data is received for each
SIM. Aspects of the present disclosure are related to such
scenarios in which UEs are required to acknowledge the received
data.
BRIEF DESCRIPTION OF THE VIEWS OF DRAWINGS
Example aspects of the present disclosure will be described with
reference to the accompanying drawings briefly described below.
FIG. 1 is a block diagram of an example environment in which
several aspects of the present disclosure can be implemented.
FIG. 2 is a flow-chart illustrating the manner in which
acknowledgements to received sub-frames in a multi-SIM user
equipment are transmitted using a shared transmit chain when
receiving data continuously on each SIM, according to an aspect of
the present disclosure.
FIG. 3 is a block diagram illustrating the details of a user
equipment (UE) in an aspect of the present disclosure.
FIG. 4 is a block diagram depicting a protocol stack implemented in
a UE in an aspect of the present disclosure.
FIG. 5 is an example timing diagram illustrating an example
scenario of a UE multiplexing a shared transmit chain for
transmitting acknowledgments to receipt of multiple concurrent and
continuous sequences of sub-frames, in an aspect of the present
disclosure.
FIG. 6 is an example timing diagram illustrating another example
scenario of a UE multiplexing a shared transmit chain for
transmitting acknowledgments to receipt of multiple concurrent and
continuous sequences of sub-frames, in an aspect of the present
disclosure.
FIG. 7 is a diagram of a table containing throughput loss values
for various combinations of transmit window size and retransmission
limits maintained in a UE, in an aspect of the present
disclosure.
In the drawings, like reference numbers generally indicate
identical, functionally similar, and/or structurally similar
elements. The drawing in which an element first appears is
indicated by the leftmost digit(s) in the corresponding reference
number.
DETAILED DESCRIPTION
1. Overview
UEs are often provided with subscriber identity modules (SIMs). A
SIM typically contains various information such as telephone
number, the international mobile subscriber identity (IMSI) number
(also the phone number) used by a service provider to identify and
authenticate a subscriber, security keys, temporary information
related to the local network, a list of the services provided by
the service provider, etc.
A single UE may be provided with multiple SIMs, for example, to
facilitate the UE to communicate with two different telephone
networks (service providers). In such UEs, multiple SIMs may be
designed to share a same transmit chain (including a portion
thereof, within the transceiver) for reasons such as cost and
power-savings. As is also well known in the relevant arts, a
transmit chain is used for modulating a carrier with information
bits and translating the modulated carrier to a desired frequency
band for transmission on a wireless medium at a desired power
level.
Frames are employed for synchronization and coordination of
transmission in wireless telephone networks at a physical layer
level as is also well known in the relevant arts. Frames may
contain sub-frames, with each sub-frame being used for transmitting
a sequence of symbols which are error-coded (e.g., with CRC for
each sub-frame). For example, in the LTE FDD standard, a frame may
span 10 milli-seconds split as 10 sub-frames, each of one
milli-second duration.
A UE may receive data (in the form of sub-frames) continuously on
each of the respective multiple SIMs. The term `continuously`
implies successive sub-frames are received in consecutive sub-frame
intervals carrying data portions spanning one or more frames
allocated for reception by the same SIM. For example, when a UE
receives video data, the corresponding data units may be received
continuously.
UEs are often required to generate acknowledgements with respect to
individual sub-frames to enable flow-control and retransmissions
when required. A positive acknowledgement ACK is sent to indicate
that a corresponding sub-frame was accurately received, while a
negative acknowledgement NACK is used to indicate error in
reception of the corresponding sub-frame.
Standards may specify the maximum duration by which an ACK is to be
successfully received by the sender (here base station) after which
a sender may retransmit the data corresponding to the
unacknowledged sub-frame. It may be desirable to reduce such
retransmissions for reasons such as higher effective data
throughput.
Aspects of the present disclosure are accordingly applicable when
multiple SIMs of a user equipment are able to concurrently receive
sub-frames while only one of the SIMs can transmit data on a
wireless medium in any sub-frame interval. In an aspect of the
present disclosure, a UE checks whether each of the (e.g., two)
SIMs has received sub-frames in successive intervals prior to a
current interval. If such a condition is satisfied by all the SIMs,
the UE allocates several successive (transmit) intervals to the
first SIM before allocating next successive (transmit) intervals to
another SIM.
If such a condition is not satisfied, the sub-frame intervals may
be allocated according to any other approach (i.e., not constrained
by the requirement of successive sets of transmit intervals to the
two SIMs) as suited for the specific situation. The allocated
sub-frame intervals are used to send the acknowledgements of the
previously received sub-frames. By having allocated successive sets
of transmit intervals to each SIM, the number of acknowledgements
which are not transmitted timely (causing the sender to retransmit
the corresponding frames) are reduced.
According to an aspect of the present disclosure, each of the SIMs
is allocated an equal number of successive sub-frame intervals,
which is a multiple of 8 or one less thereto.
Several aspects of the disclosure are described below with
reference to examples for illustration. It should be understood
that numerous specific details, relationships, and methods are set
forth to provide a full understanding of the disclosure. One
skilled in the relevant arts, however, will readily recognize that
the disclosed features can be practiced without one or more of the
specific details, or with other methods, etc. In other instances,
well-known structures or operations are not shown in detail to
avoid obscuring the features of the disclosure.
2. Example Environment
FIG. 1 is a block diagram representing an example environment in
which several aspects of the present disclosure can be implemented.
The example environment is shown containing only representative
devices and systems for illustration. However, real world
environments may contain more or fewer systems/devices. FIG. 1 is
shown containing a cell 100 of a cellular network. Cell 100 is
shown containing base station 110 and user equipment (UE) 120, UE
130 and UE 140. Cell 100 and the devices therein may operate
according to any of well-known standards/specifications for
wireless mobile communications such as, for example, GSM (Global
System for Mobile communication), LTE (Long Term Evolution,
including both Frequency Division Duplex and Time Division Duplex),
etc.
Base station 110 is a fixed communications unit and provides the
last-mile (or last hop) communications link to UEs in the cell.
Although not shown in FIG. 1, base station 110 may be connected to
other devices/systems in the cellular network infrastructure to
enable UEs in cell 100 to communicate with devices (e.g., other
UEs) in other cells, with landline communications equipment in a
conventional PSTN (Public Switched Telephone Network), public data
networks such as the internet etc. In the context of LTE, base
station 110 is referred to as eNodeB. Although noted as a base
station, base station 110 can also correspond to a macrocell,
microcell or a femtocell. Macro/micro/femtocells are special
cellular base stations (operating over small cell areas) that are
often deployed in small areas to add extra cell capacity. For
example, such small cells can be deployed temporarily during
sporting events and other occasions where a large number of cell
phone users are expected to be concentrated in one spot.
While only one base station is shown in FIG. 1 for simplicity, the
environment of FIG. 1 can have multiple base stations with
overlapping coverage as well. In such situations, a UE may be able
to connect with (and exchange data/voice) with each of the multiple
base stations if the UE is equipped to operate with a corresponding
number of SIMs.
UE 120, UE 130 and UE 140 represent wireless devices such as mobile
phones, and may be used for wireless communication such as voice
calls, data exchange such as web browsing, receiving and sending
emails, etc. A UE (e.g., UE 120) may be equipped with multiple
(e.g., two) SIMs, thereby enabling the UE to simultaneously and
continuously receive data for each of the multiple SIMs (all from a
same base station or from respective bases stations). The multiple
SIMs may permit access to either the same type of radio access
technique (e.g., both SIMs are for LTE networks), or for dissimilar
radio access techniques (e.g., one SIM for LTE and the other SIM
for 2G, one SIM for LTE and the other SIM for 3G, one SIM for LTE
and the other SIM for 5G, etc.
The UE may need to transmit acknowledgements to the respective (or
same) base stations upon receipt of data units received by each of
the SIMs, in the manner specified by the communication standard
(e.g., LTE) to which the UE (and the environment of FIG. 1)
conform.
However, as noted above, for reasons such as cost, power
consumption etc., a UE may be implemented to have only a limited
number (e.g., only one transmit chain shared by two SIMs) of
transmit chains. Accordingly, the UE may need to schedule the
acknowledgements for transmission to the respective base station
using a shared transmit chain. The manner in which such scheduling
is achieved is described next with respect to a flowchart.
3. Multiplexing a Transmit Chain
FIG. 2 is a flowchart illustrating the manner in which
acknowledgements to received sub-frames in a multi-SIM user
equipment are scheduled using a shared transmit chain when
receiving data continuously on each SIM (Subscriber Identity
Module). The flowchart is described with respect to the environment
of FIG. 1, and in relation to UE 120, merely for illustration.
However, various features described herein can be implemented in
other environments and using other components as well, as will be
apparent to one skilled in the relevant arts by reading the
disclosure provided herein. Further, the steps in the flowchart are
described in a specific sequence merely for illustration. The
flowchart starts in step 201, in which control passes immediately
to step 210.
In step 210, UE 120 receives concurrently a first sequence of
frames on a first SIM and a second sequence of frames on a second
SIM. The frames are received concurrently (or simultaneously) in
view of the presence of two independent receivers (in UE 120),
which can receive packets on the corresponding two SIMs
independently. Control then passes to step 220.
In step 220, UE 120 determines whether frames in each of the
sequences are received in respective successive sub-frame intervals
(i.e., continuously). In other words, determination is made as to
whether the first sequence of frames are received in successive
sub-frame intervals, and whether the second sequence of frames also
satisfies the same condition. Control transfers to step 230 if both
sequences satisfy the condition, and to step 260 otherwise.
In step 230, UE 120 allocates successive sequences of sub-frame
intervals to the first SIM for transmitting acknowledgements and/or
data, and in step 250 UE 120 allocates following successive
sequences of sub-frame intervals to the second SIM for transmitting
acknowledgements and/or data. Control then transfers to step
270.
In step 260, UE 120 allocates sub-frame intervals to the two SIMs
according to another approach in which the sub-frame intervals need
not be successive. In other words, such approach can be suited for
the corresponding situations. For example, a goal may be to
acknowledge the packets soon (contrasted with the delays that would
occur with some of the acknowledgement when steps 230 and 250
operate) so that buffering is reduced at the sender and subsequent
packets are forwarded quickly.
In step 270, UE 120 acknowledges the received frames in the
allocated intervals. As will be clear from the description below,
steps 230 and 250 operate to reduce the loss of acknowledgements
(when the condition of step 220 is met) at least in environments
such as LTE (and when at least one sub-interval is used to switch
transmit allocation from one SIM to the other), while step 260
leaves open alternative approaches to transmit allocation as suited
for the specific situation. In one such alternative approach noted
below, when the sub-frames are received in sparse intervals, the
allocation of the shared transmit chain is switched more frequently
to attempt to send the acknowledgement in the very first transmit
opportunity. Control then passes to step 210, and the corresponding
steps of the flowchart may then be executed.
The features thus described can be implemented in various
implementations to address corresponding situations. The
description is continued with respect to the details of an example
implementation of UE 120.
4. User Equipment
FIG. 3 is a block diagram depicting the implementation details of a
UE in an aspect of the present disclosure. UE 120 is shown
containing processing block 310, non-volatile memory 320,
input/output (I/O) block 330, random access memory (RAM) 340,
real-time clock (RTC) 350, SIM1 360A, SIM2 360B, transmit (TX)
block 370, receive (RX) blocks 380A and 380B, switch 390, and
antennas 395A and 395B. Some or all units of UE 120 may be powered
by a battery (not shown).
In another aspect of the present disclosure, UE 120 is
mains-powered and contains corresponding components such as
regulators, power filters, etc. The specific blocks of UE 120 are
shown by way of illustration only, and UE 120 may contain more or
fewer blocks depending on specific requirements. According to yet
another aspect, UE 120 corresponds to a dual-SIM mobile phone that
is implemented to operate according to LTE specifications in
Frequency Division Duplex (FDD) mode as well as Time Division
Duplex (TDD) mode.
In the description below, however, it is assumed that UE 120 is
operated in LTE FDD mode. However, in other aspects, UE 120 may
correspond in general to multi-SIM mobile phone capable of
operating according to other radio access technologies (such as,
for example, GSM, 3G, 5G, etc.) as well.
Each of SIM1 360A and SIM2 360B represents a subscriber identity
module (SIM) that may be provided by a service provider. As is well
known in the relevant arts, a SIM may store the international
mobile subscriber identity (IMSI) number (also the phone number)
used by a service provider to identify and authenticate a
subscriber. Additionally, a SIM may store address book/telephone
numbers of subscribers, security keys, temporary information
related to the local network, a list of the services provided by
the service provider, etc. Though not shown, the UE is equipped
with two holders, each for housing a respective one of the two SIMs
360A and 360B. Typically, the SIM is `inserted` into such housing
before the UE can access the services provided by the network
operator for subscriber configured on the SIM.
Processing block 310 may read the IMSI number, security keys etc.,
in transmitting and receiving voice/data via TX block 370 and RX
blocks 380A/380B respectively. SIM1 and SIM2 each enable UE 120 to
subscribe to respective LTE services (data, voice, etc.) according
to both FDD and/or TDD.
RTC 350 operates as a clock, and provides the `current` time to
processing block 310. Additionally, RTC 340 may internally contain
one or more timers. I/O block 330 provides interfaces for user
interaction with UE 120, and includes input devices and output
devices. The input devices may include a keypad and a pointing
device (e.g., touch-pad). Output devices may include a display with
touch-sensitive screen.
Antenna 396 operates to receive from a wireless medium,
corresponding wireless signals (representing voice, data, etc.)
according to one or more standards such as LTE, and provides the
received wireless signals to RX block 380A. Antenna 396 may also be
connected via a switch to a transmit block (such as TX block 370
described below), but such blocks and connections are not shown in
FIG. 3 in the interest of conciseness.
Antenna 395 operates to receive from, and transmit to, a wireless
medium, corresponding wireless signals (representing voice, data,
etc.) according to one or more standards such as LTE. Switch 390
may be controlled by processing block 310 (connection not shown) to
connect antenna 395 to one of blocks 370 and 380B as desired,
depending on whether transmission or reception of wireless signals
is required. Switch 390, antenna 395 and the corresponding
connections of FIG. 3 are shown merely by way of illustration.
Instead of a single antenna 395, separate antennas, one for
transmission and another for reception of wireless signals, can
also be used. Further, although separate antennas 395 and 396 are
shown in FIG. 3, a single antenna can instead be used using
appropriate techniques, as would be apparent to one skilled in the
relevant arts.
Each of RX blocks 380A and 380B represents a receiver (or receive
chain) that receives a corresponding wireless (RF) signal bearing
voice/data and/or control information via the corresponding
antennas and switches, demodulates the RF signal, and provides the
extracted voice/data or control information to processing block
310. RX blocks 380A and 380B each may contain RF circuitry
(front-end filter, low-noise amplifier, mixer/down-converter,
filters) as well as baseband processing circuitry for demodulating
the down-converted signal. Alternatively, RX blocks 380A and 380B
may contain only the RF circuitry, with processing block 310
performing the baseband operations in conjunction with the RF
circuitry. Data/voice for SIM1 and SIM2 are received via RX blocks
380A and 380B respectively.
According to aspects of the present disclosure, UE 120 may
concurrently receive data continuously (as against intermittently)
for SIM1 via RX block 380A and data for SIM2 via RX block 380B. UE
120 transmits acknowledgements to the receive data for each SIM by
time-multiplexing shared transmitter TX block 370 (or transmit
chain as noted below) according to the flowchart of FIG. 2, as
described in detail below.
TX block 370 (which represents a shared transmit chain) receives,
from processing block 310, digital signals representing information
(voice, data, acknowledgements to received data, etc.) to be
transmitted on a wireless medium (e.g., according to the
corresponding standards/specifications), generates a modulated
radio frequency (RF) signal (according to the standard), and
transmits the RF signal via switch 390 and antenna 395. TX block
370 may contain RF circuitry (mixers/up-converters, local
oscillators, filters, power amplifier, etc.) as well as baseband
circuitry for modulating a carrier with the baseband information
signal.
Alternatively, TX block 370 may contain only the RF circuitry, with
processing block 310 performing the modulation and other baseband
operations (in conjunction with the RF circuitry). TX block 370 (or
the transmit chain in general) may additionally include shared
memory resources and software modules used in the transmit
operations. In particular, and as described in detail below, TX
block 370 is multiplexed by UE 120 to transmit acknowledgments to
sub-frames received for SIM1 360A and SIM2 360B via RX block 380A
and RX block 380B respectively.
Sharing of TX block 370 (the share transmit chain) may be achieved
by processing block 310 tuning (via control signal in path 317) TX
block 370 to the corresponding frequency band (or channel) that is
desired for transmitting the respective acknowledgements (or data).
Typically, such tuning involves changing the frequency of the local
oscillators and filter pass bands in the transmit chain such that
the transmitted signal (at antenna 395) lies in the desired
frequency band.
Thus, in the context of LTE FDD, for transmitting acknowledgements
to sub-frames received by SIM1 (via RX block 380A), processing
block 310 tunes the transmit chain to cause the transmitted
wireless signal to lie in one (desired) frequency band, and for
transmitting acknowledgements to sub-frames received by SIM2 (via
RX block 380B), processing block 310 tunes the transmit chain to
cause the transmitted wireless signal to lie in another (desired)
frequency band. In the context of LTE TDD, such tuning as noted
above may not be required, and processing block 310 may merely
assign the transmit chain (without tuning) to the corresponding
transmit operations for the respective SIM.
Non-volatile memory 320 is a non-transitory machine readable
medium, and stores instructions, which when executed by processing
block 310, causes UE 120 to operate as described herein. In
particular, the instructions enable UE 120 to operate as described
with respect to the flowchart of FIG. 2. The instructions may
either be executed directly from non-volatile memory 320 or be
copied to RAM 340 for execution.
RAM 340 is a volatile random access memory, and may be used for
storing instructions and data. RAM 340 and non-volatile memory 320
(which may be implemented in the form of read-only
memory/ROM/Flash) constitute computer program products or machine
(or computer) readable medium, which are means for providing
instructions to processing block 310. Processing block 310 may
retrieve the instructions, and execute the instructions to provide
several features of the present disclosure.
Processing block 310 (or processor in general) may contain multiple
processing units internally, with each processing unit potentially
being designed for a specific task. Accordingly, processing block
310 may be implemented as separate processing cores, one each to
handle operations for each SIM. Alternatively, processing block 310
may contain only a single general-purpose processing unit, and
operations for each SIM may be handled by respective execution
threads (software instructions) executed using processing block
310. Among other operations, processing block 310 enables
acknowledgements to sub-frames received by SIM1 and SIM2 by
operating the transmit chain in a time multiplexed fashion
according to the flowchart of FIG. 2, and as illustrated below.
Further, processing block 310 applies error correction or detection
techniques to determine if each sub-frame received by SIM1 and SIM2
has any error or not, and accordingly schedules either a (positive)
ACK (in case of no error) or a NACK (in case of error) for
transmission to the corresponding base station(s). In general,
processing block 310 executes instructions stored in non-volatile
memory 350 or RAM 340 to enable UE 120 to operate according to
several aspects of the present disclosure, described in detail
herein.
FIG. 4 illustrates an alternative view of the implementation of UE
120, and shows an example protocol stack implemented in UE 120 for
handling operations for one SIM. Protocol stack 400, which is
assumed to handle operations for SIM2 360B is shown containing
layers L1, L2, L3 and the application layer. The various layers in
stack 400 may be implemented to generally conform to the ISO OSI
(International Standards Organization Open Systems Interconnect)
model, and are only briefly described below, since the
corresponding implementations of the blocks would be well known to
one skilled in the relevant arts on reading the disclosure
herein.
Further, only the relevant blocks of the protocol stack are shown
in FIG. 4, and typically more blocks (such as transport layer etc.)
according to the ISO OSI model may be present, as also would be
apparent to one skilled in the relevant arts. Although not shown in
FIG. 4 in the interest of conciseness, UE 120 may have another
protocol stack, similar to stack 400, for handling the operations
corresponding to SIM1 360A. Alternatively, protocol stack 400 may
be designed to handle operations for both SIMs. It is assumed
herein that UE 120 is implemented to have separate stacks for each
of the two SIMs.
In stack 400, Layer 1 corresponds to PHY 410, which represents the
electrical and physical interface between UE 120 and a transmission
medium (here a wireless medium). PHY 410 receives data from MAC 420
and forwards the data to antenna 395 for transmission. PHY 410
receives data from antenna 395 and forwards the data to MAC 420 for
further processing. PHY 410 includes TX block 370 and RX block
380B. Although TX block 370 is shown as part of the protocol stack
for SIM2 in the interest of simplifying the description, TX block
370 is controlled by a software component (executed by processing
block 310) to transmit acknowledgements/data either for SIM1 or
SIM2.
Layer 2 includes MAC (Medium Access Control layer) 420, Radio Link
Control layer (RLC) 430 and Packet Data Convergence Protocol (PDCP)
440. MAC 420 performs operations such as mapping between logical
channels and transport channels, error correction through HARQ,
priority handling between logical channels, etc. In particular, MAC
420 is designed to transmit HARQ acknowledgements (ACK/NACK noted
above) to sub-frames received by SIM2. The MAC layer in the
protocol stack for SIM1 is designed to transmit acknowledgements
(ACK/NACK noted above) to sub-frames received by SIM1. NACKs, as
well as absence of an acknowledgement for a sub-frame, causes the
sender base station 110 to retransmit the corresponding
sub-frame.
The HARQ acknowledgements by the respective MAC layers is achieved
in the form of processing block 310 operating the shared transmit
chain to schedule and transmit the respective acknowledgements.
Alternatively, dedicated hardware may be contained in the transmit
chain for transmitting the HARQ response, with processing block 310
merely scheduling the dedicated hardware for transmitting the
respective HARQ responses.
RLC 430 performs operations such as error correction through ARQ,
concatenation, segmentation and reassembly of RLC SDUs,
re-segmentation of RLC data PDUs, duplicate detection, etc. When
packets are deemed to be lost at the PHY/MAC level, RLC 430 (and
the RLC layer for SIM1) may operate to recover the packet using the
ARQ mechanism. PDCP 440 performs operations such as header
compression and decompression, ciphering and deciphering, etc.
Layer 3 includes RRC (Radio Resource Control layer) 450 and NAS
(Non-access Stratum protocol) 460. RRC 450 performs operations such
as paging, establishment, maintenance and release of an RRC
connection between UE 120 and the corresponding base station,
security functions including key management, QoS (Quality of
Service) management functions, measurement reporting and control of
the reporting, etc. NAS 460 performs operations such as support of
mobility of UE 120, support of session management procedures to
establish and maintain IP connectivity between UE 120 and a packet
data network gateway, etc.
Application layer 470 represents a communications component that
allows software applications executing in UE 120 to communicate
with software applications in other nodes (servers, etc.) via the
other blocks shown in FIG. 4.
The description is continued with examples illustrating the manner
in which acknowledgements to received sub-frames in a multi-SIM
user equipment are scheduled using a shared transmit chain when
receiving data continuously on each SIM.
5. Illustrative Examples
In an aspect of the present disclosure implemented in the context
of LTE FDD, UE 120 receives data continuously and concurrently, on
both SIM1 and SIM2, and uses a shared transmit chain for
transmitting HARQ acknowledgments to the received data. Data from a
base station is transmitted to UE 120 in units referred to as
sub-frames, each sub-frame being 1 milli-second (ms) long, and
termed a TTI (Transmission Time Interval). Data frames (or
acknowledgements) from UE 120 are also transmitted in units of 1 ms
sub-frames.
In LTE FDD, there are typically eight processes (software execution
entities) in each of the uplink (UE 120 to base station) and
downlink (base station to UE 120) directions. A process in the base
station sends data in a sub-frame to UE 120, and goes into inactive
state till an ACK or NACK is received from the UE. In response to
receipt of the data sent at sub-frame `n`, the UE is expected to
transmit an ACK/NACK (HARQ acknowledgement) to the packet at
(n+4).sup.th sub-frame. Depending on whether ACK or NACK is
received, the base station either transmits a next packet (in case
of ACK) or re-transmits the earlier packet (in case of NACK or no
response at all (i.e., neither ACK nor NACK)) at (n+8).sup.th
sub-frame. Though described in terms of number of processes, it
will be evident to one skilled in the relevant arts that the number
8 of the illustrative example represents a window/buffer size in
terms of a maximum number of sub-frames which can be unacknowledged
after having been transmitted, at any moment.
Assuming there are eight processes on the base station (as in LTE),
each process waits for 8 ms before sending a next sub-frame (or a
re-transmission of the previous unacknowledged data) over the
wireless medium. Each process maintains a corresponding transmit
buffer. A process maintains transmitted data in the corresponding
transmit buffer till an ACK is received or a pre-determined number
of retransmissions is crossed. Receipt of a NACK causes the process
to retransmit the data in a corresponding sub-frame. New data is
sent by a process once its transmit buffer is empty.
Similarly, UE 120 may also implement 8 processes (per SIM) in the
uplink direction. Each process (of the 8 processes) at UE 120 also
waits for 8 ms before transmitting a next acknowledgment, or
retransmitting the same acknowledgment in the event the
acknowledgment could not be or was not sent. Each of the eight
processes (per SIM) at UE 120 maintains a corresponding transmit
buffer. A process retains an acknowledgement in its transmit buffer
until the acknowledgment is transmitted.
If a process could not transmit an acknowledgement in a scheduled
sub-frame (referred to herein as a transmission opportunity), the
process `re-transmits` the acknowledgment in the sub-frame
occurring 8 ms later (the next transmission opportunity) according
to LTE specification. The maximum number of transmission
opportunities for a process is predetermined, and communicated by
the base station to UE 120 via an RRC Connection Reconfiguration
message. The MAC layers in the respective protocol stacks
corresponding to SIM1 and SIM2 manage the HARQ processes for each
SIM.
It should be appreciated that the acknowledgements can be in the
form of stand-alone sub-frames, though they can be piggy-backed on
uplink data transmitted in the same sub-frame. Accordingly the
description below is provided with respect to transmission of
acknowledgments only. In an aspect, UE 120 alternately allocates
the transmit chain for transmitting acknowledgements to data
received for SIM1 and SIM2, with each allocation duration being
termed a transmission window size (TWS).
FIG. 5 is an example timing diagram showing the receipt of
sub-frames by SIM1 and SIM2, and the corresponding HARQ responses
transmitted by the shared transmit chain, when maxHARQ-Tx has a
value of 2, and TWS is 8 ms. The parameter maxHARQ-Tx is the
maximum number of transmissions of a same data (or acknowledgement)
permitted by UE 120 in the uplink before transmission of that data
(or acknowledgement) is deemed to have failed. Illustration for
another set of values of TWS and maxHARQ-Tx, as well as the
calculation for obtaining TWS from maxHARQ-Tx is provided in
sections below.
In FIG. 5, timing sequence SIM1-Rx (510) represents a sequence of
successive sub-frames received for SIM1 (360A), while timing
sequence SIM2-Rx (530) represents a sequence of sub-frames received
concurrently for SIM2 (360B). The sub-frames on SIM1-Rx 510 are
received in successive intervals (i.e., continuously) because there
is no sub-interval in which a sub-frame is absent. Thus, if a
sub-frame were to be absent in one of the sub-intervals, the
`successive sub-frames` condition would not be met and the
sub-frames are not received continuously.
Timing sequences SIM1-Tx (520) and SIM2-Tx (540) respectively
represent transmissions of corresponding acknowledgments to the
downlink data received by SIM1 and SIM2 respectively. In FIG. 5,
transmissions (or scheduled transmissions which are not yet sent)
are denoted by numbers (0, 1, 2, etc.) while retransmissions (or
delayed transmissions) are denoted by numbers with an R prefix (R0,
R1, etc.). Each box (e.g., 0, 1, R0, R7, etc.) in a timing sequence
represents a TTI and is 1 ms long. Intervals t52-t53, t53-t54 and
t54-t55 are each 8 ms long, and represent corresponding TWS. It is
assumed that 1 ms of time is lost in switching the shared transmit
chain for use by one SIM to the other. Further, it is assumed that
a sub-frame when received is received without errors, and thus only
corresponding ACKs are always noted as being transmitted.
In FIG. 5, SIM1 is shown as receiving four sub-frames (denoted 0,
1, 2 and 3) in time interval t51-t52, and SIM2 is also shown as
receiving four sub-frames (denoted 0, 1, 2 and 3). The four
sub-frames each represent respective sequences of frames received
concurrently by SIM1 and SIM2 (step 210). Since both the sequences
are continuous and concurrent (step 220 evaluates true), UE 120
allocates a sequence of eight successive sub-frames in interval
t52-t53 to SIM1 for transmission of acknowledgements (step 230),
and a next sequence of eight successive sub-frames in interval
t53-t54 to SIM2 for transmission of acknowledgements (step
250).
Thus, the shared transmit chain of UE 120 transmits seven
acknowledgements (denoted as 0, 1, 2, 3, 4, 5, and 6) to respective
ones of received sub-frames 0, 1, 2, 3, 4, 5 and 6, each
acknowledgement being 4 ms later than the corresponding receipt of
data. Thus, arrow 551 shows the acknowledgement to received
sub-frame 0. However, since 1 ms is lost in switching the transmit
chain for use by SIM2 (starting from t53), UE 120 cannot transmit
the acknowledgment 7 (marked with a cross to indicate it was not
transmitted) corresponding to received sub-frame 7 (as indicated by
arrow 552). Since in interval t52-t53, the transmit chain is
allocated to SIM1, SIM 2 cannot use the transmit chain for
transmitting acknowledgements to received data 0, 1, 2, 3, 4, 5, 6
and 7, and these slots are marked with `strike out` in timing
sequence 540 to indicate they could not be transmitted. Since the
base station does not receive any acknowledgement for the
transmitted data 0-7 for SIM2, the base station retransmits these
sub-frames (denoted as R0-R7).
UE 120 allocates the shared transmit chain to SIM2 in interval
t53-t54. Thus, starting at t53, the transmit chain transmits
delayed acknowledgements R0 through R6 for the received
re-transmitted data R0 through R6. Arrow 561 indicates that
acknowledgement 7 is to be sent for received sub-frame 7. However,
since 1 ms is lost in switching the transmit chain for use by SIM2
(starting from t53), UE 120 cannot transmit the acknowledgment 7
(marked with a cross to indicate it was not transmitted). In
interval t53-t54, the shared transmit chain of UE 120 transmits
seven acknowledgements (denoted as R0, R1, R2, R3, R4, R5, and R6)
to respective ones of received re-transmitted sub-frames R0, R1,
R2, R3, R4, R5 and R6, each acknowledgement being 4 ms later than
the corresponding receipt of data.
However, since 1 ms is lost in switching the transmit chain for use
by SIM1 (starting from t54), UE 120 cannot transmit the
acknowledgment R7 (marked with a cross to indicate it was not
transmitted) corresponding to received re-transmitted sub-frame R7
(as indicated by arrow 553).
Since in interval t53-t54, the transmit chain is allocated to SIM2,
SIM1 cannot use the transmit chain for transmitting
acknowledgements to received data 0, 1, 2, 3, 4, 5, 6 and R7, and
these slots are marked with `strike out` to indicate they could not
be transmitted. In particular, since the base station has
transmitted sub-frame 7 twice, and since no acknowledgement was
received from UE 120 (arrows 552 and 553 indicate no ACK was sent),
sub-frame 7 is lost (i.e., is not retransmitted further by the
corresponding process at the base stations. Sub-frame 7 can be
recovered by RLC layer of SIM1 using ARQ.
Similarly, since no acknowledgement was received from UE 120 for
sub-frame 7 and retransmitted sub-frame R7 for SIM2, (arrows 561
and 563 indicate no ACK was sent), sub-frame 7 of SIM 2 is also
lost, but can possibly be recovered by RLC layer of SIM2.
UE 120 checks again at t54 whether continuous (successive)
sub-frames for SIM1 and SIM2 have been received concurrently
immediately prior to (current time) t54. Since such a check
evaluates true, UE 120 allocates the shared transmit chain to SIM1
in interval t54-t55, and the subsequent interval (end of this
interval not shown in FIG. 5) to SIM2. Arrow 554 indicates
acknowledgement R0 for received re-transmitted sub-frame R0. Arrow
555 indicates that acknowledgement 7 is to be sent for received
original sub-frame 7. However, since 1 ms is lost in switching the
transmit chain for use by SIM2 (starting from t55), UE 120 cannot
transmit the acknowledgment 7 (marked with a cross to indicate it
is not transmitted).
In interval t54-t55, the shared transmit chain of UE 120 transmits
seven acknowledgements (denoted as R0, R1, R2, R3, R4, R5, and R6)
to respective ones of received re-transmitted sub-frames R0, R1,
R2, R3, R4, R5 and R6, each acknowledgement being 4 ms later than
the corresponding receipt of data. Since in interval t54-t55, the
transmit chain is allocated to SIM1, SIM 2 cannot use the transmit
chain for transmitting acknowledgements to received data 0, 1, 2,
3, 4, 5, 6 and 7, and these slots are marked with `strike out` to
indicate they could not be transmitted.
UE 120 allocates the shared transmit chain to SIM2 for 8 ms
interval starting at t55. Arrows 565 and 566 respectively indicate
that acknowledgements R0 and R6 are transmitted in response to
re-transmitted sub-frames R0 to R6 for SIM2. Sub-frame 7 is again
lost. No acknowledgements are sent for SIM1 in the 8 ms duration
starting at t55. UE 120 repeats the above allocations of the
transmit chain in alternate 8 ms intervals to SIM1 and SIM2. One
sub-frame out of 8 sub-frames is lost due to the multiplexing of
the transmit chain.
FIG. 6 is an example timing diagram showing the receipt of
sub-frames by SIM1 and SIM2, and the corresponding HARQ responses
transmitted by the shared transmit chain, when maxHARQ-Tx has a
value of 3, and TWS is 15 ms. Again, it is assumed that
transmissions (or scheduled transmissions which could not be sent)
are denoted by numbers (0, 1, 2, etc.) while re-transmissions (or
delayed transmissions) are denoted by numbers with an R prefix (R0,
R1, etc.). Each box (e.g., 0, 1, R0, R7, etc.) in a timing sequence
represents a TTI and is 1 ms long. Intervals t62-t63, t63-t64 and
t64-t65 are each 15 ms long, and represent corresponding TWS. It is
assumed that 1 ms of time is lost in switching the shared transmit
chain for use by one SIM to the other. It is assumed that a
sub-frame when received is received without errors, and thus only
corresponding ACKs are always noted as being transmitted.
UE 120 is shown as allocating the transmit chain in time intervals
t62-t63, t63-t64 and t4-t65 alternately for transmitting
acknowledgements to sub-frames received by SIM1, SIM2 and SIM1. The
operation of the transmit chain is similar to the description
provided with respect to FIG. 5, except for the difference in TWS
and maxHARQ-Tx, and is not provided here in the interest of
brevity. However, it may be observed that no sub-frames (or data in
general) is lost by either SIM1 or SIM2, since each received
sub-frame is acknowledged within 3 transmit opportunities. In
timing sequence 620, sub-frame 6 which could not be acknowledged
(due to switching time incurred in switching the transmission chain
to SIM2 at t63) in the first and second transmission opportunities
(as indicated by arrows 651 and 652 respectively) is acknowledged
at the third transmission opportunity (indicated by arrow 653).
Similarly, in timing sequence 640, sub-frame 5 which could not be
acknowledged (due to switching time incurred in switching the
transmission chain to SIM1 at t64) in the first and second
transmission opportunities (as indicated by arrows 661 and 662
respectively) is acknowledged at the third transmission opportunity
(indicated by arrow 663)
With respect to FIG. 5 and FIG. 6, it is noted that if the
concurrently received sub-frames are not continuous (step 220 of
FIG. 2 evaluates false), then UE 120 may allocate respective
sub-frame intervals to the two SIMS for transmitting the
acknowledgments using the shares transmit chain using some other
approach (step 260) which does not require the allocated sub-frame
intervals to be successive. For example, if only a sparse number of
sub-frames are received for each SIM, then UE 120 may multiplex the
shared transmit chain to ensure that an acknowledgement to each
sub-frame is always sent the first transmission opportunity, i.e.,
4 sub-frames later (rather than missing some transmission
opportunities as in the examples of FIG. 5 and FIG. 6).
Based on simulations, and also on the fact that base stations (such
as base station 110) and UE 120 each use 8 HARQ processes, it has
been observed that TWS values which are equal to, or very nearly
equal to (shown as 1 less than the multiple), multiples of 8 of the
maxHARQ-Tx values may provide satisfactory performance in terms of
throughput loss when multiplexing a shared transmit chain to
transmit acknowledgements. In an aspect, UE 120 uses 8 ms, 15 ms,
23 ms, 31 ms, 39 ms, 63 ms, 71 ms, 79 ms and 87 ms as possible
values for TWS. TWS values of 47 ms and 55 ms are not used since
with these values of TWS there is a substantial likelihood of one
SIM losing synchronization with its downlink data by not being able
to send 60 acknowledgements in 150 ms (required by the LTE
standard, as also noted below). UE 120 maintains a table (700 of
FIG. 7) containing percentage loss of data (i.e., percentage loss
in throughput) in the downlink direction for the above-noted values
of TWS for various values of maxHARQ-Tx (or retransmission limit,
in general), as shown in FIG. 7.
In FIG. 7, row R1 lists the above-noted values of TWS (in ms),
while column C1 lists example values of maxHARQ-Tx. The
intersection of each of the other columns and rows lists the
corresponding value of throughput loss for the corresponding value
of TWS and maxHARQ-Tx. As an example, the intersection of R2 and C2
lists the throughput loss for a maxHARQ-Tx of 2 and TWS of 8 ms.
When the SIM1 and SIM2 are associated with different maxHARQ-Tx
values for transmission in the uplink, then TWS value calculated
based on the lesser of the two maxHARQ-TX values, i.e., based on
MIN (maxHARQ-Tx.sub.SIM1, maxHARQ-Tx.sub.SIM2), wherein MIN is the
`minimum` operator, maxHARQ-Tx.sub.SIM1 is the maxHARQ-Tx value
associated with SIM1, maxHARQ-Tx.sub.SIM2 is the maxHARQ-Tx value
associated with SIM2, with the specific manner in which TWS is
calculated being as described herein.
The throughput loss values of the table of FIG. 7 are obtained in
the following manner.
For values of a variable HARQretransmissiontime that are equal to
TWS, and for values of TWS not equal to 8 ms, the throughput loss
can be calculated as: Throughput loss=ceil[(0.5)*100]/TWS Equation
1
wherein, ceil ( ) represents an operation defined as
ceiling(x)=smallest integer greater than or equal to x, and
wherein HARQretransmissiontime=(([maxHARQ-Tx)-1]*8).
For values of HARQretransmissiontime that are less than TWS, and if
TWS equals 8 ms, the throughput loss can be calculated as:
Throughput loss-(floor((TWS+1)/(maxHARQ-Tx*8))*8)*100/TWS Equation
2
wherein floor ( ) represents an operation defined as
floor(x)=largest integer less than or equal to x.
For example, for TWS=15 ms, and maxHARQ-Tx=2, throughput loss can
be calculated as [{floor((15+1)/(2*8))*8}*100]/15, which evaluates
to 53.33%, as indicated in table of FIG. 7. For TWS=23 ms, and
maxHARQ-Tx=2, throughput loss can be calculated as
[{floor((23+1)/(2*8))*8}*100]/23, which equals 34.78%, as indicated
in table of FIG. 7.
For values of HARQretransmissiontime that are greater than TWS,
there is no throughput loss. Although throughput loss values for
only a limited set of combinations of TWS and maxHARQ-Tx values are
shown in table 700, throughput loss values for other combinations
of TWS and maxHARQ-Tx can be computed using the formulas provided
above.
For a given value of maxHARQ-Tx (which is specified by base station
110), UE 120 selects the highest value of TWS corresponding to the
given value of maxHARQ-Tx that has minimum throughput loss. As an
example, with reference to table 700, if maxHARQ-Tx is 2, then TWS
of 8 is selected. On the other hand, if maxHARQ-Tx is 5, then TWS
of 31 is selected.
It is noted here that although the above description is provided in
the context of transmission of acknowledgments, the same or similar
techniques (with corresponding appropriate modifications) can be
used when UE 120 transmits continuous sequences of uplink data
concurrently for SIM1 and SIM2 using a shared transmit chain as
well.
Thus, UE 120 minimizes throughput loss (which might otherwise lead
to loss of synchronization with downlink data on one or both SIMs)
and delays in downlink data, while multiplexing a shared
transmitter to transmit acknowledgments to received sub-frames, as
described in detail above. It is noted here that as per
Specification 36.133, section 8.1.2.2.3, of 3GPP (3.sup.rd
Generation Partnership Project), a UE is expected to transmit at
least 60 acknowledgements (ACKs or NACKs) in a duration of 150 ms,
provided there is continuous downlink data. The techniques
described above enable UE 120 to comply with the above-noted
constraint even while using a shared transmit chain. If the value
of maxHARQ-Tx were to be changed by the base station, then UE 120
would again determine the optimum value of TWS to be used based on
table 700, and change the TWS duration accordingly.
6. Conclusion
References throughout this specification to "one aspect", "an
aspect", or similar language means that a particular feature,
structure, or characteristic described in connection with the
aspect is included in at least one aspect of the present
disclosure. Thus, appearances of the phrases "in one aspect", "in
an aspect" and similar language throughout this specification may,
but do not necessarily, all refer to the same aspect.
Thus, in example 1, a wireless device receives concurrently a first
sequence of sub-frames on a first SIM and a second sequence of
sub-frames on a second SIM. The wireless device checks whether both
of the first sequence of sub-frames and the second sequence of
sub-frames have been received in successive sub-frame intervals
prior to a current interval. If both of the first sequence of
sub-frames and the second sequence of sub-frames have been received
in successive sub-frame intervals prior to the current interval,
the wireless device allocates a first sequence of successive
sub-frame intervals to the first SIM to transmit using the transmit
chain, and allocates a second sequence of successive sub-frame
intervals to the second SIM to transmit using the transmit chain,
with the second sequence of successive sub-frame intervals
following the first sequence of successive sub-frame intervals.
In example 2, the wireless device of example 1 optionally transmits
a first sequence of acknowledgements using the first SIM in the
first sequence of successive sub-frame intervals, with each of the
first sequence of acknowledgements corresponding to a respective
sub-frame of the first sequence of sub-frames. The wireless device
may also transmit a second sequence of acknowledgements using the
second SIM in the second sequence of successive sub-frame
intervals, with each of the second sequence of acknowledgements
corresponding to a respective sub-frame of the second sequence of
sub-frames.
In example 3, the wireless device of example 1 or 2 checks again at
a last sub-frame interval of the second sequence of successive
sub-frame intervals with the last sub-frame interval as the current
interval, and repeats the above noted allocating actions and the
transmitting actions if both of the first sequence of sub-frames
and the second sequence of sub-frames have been received in
successive sub-frame intervals prior to the current interval.
In example 4, the wireless device of examples 1-3 may receive the
first sequence of sub-frames and the second sequence of sub-frames
from a base station, wherein the sub-frames in each of the first
sequence of sub-frames and second sequence of sub-frames are
transmitted by a respective one of a total of N1 processes
operational in the base station, wherein each of the N1 processes,
after transmitting a corresponding sub-frame, is designed to enter
an inactive state till an acknowledgment to the corresponding
sub-frame is received from the wireless device.
In example 5, the wireless device of examples 1-4 optionally
receives from the base station a maximum number (N2) of transmit
opportunities provided to each wireless device for acknowledging a
respective sub-frame, wherein a duration of each of the first
sequence of successive sub-frame intervals and the second sequence
of sub-frame intervals is determined based on the lesser of the
values of N2 corresponding to the first SIM and the second SIM.
The features of the above examples are also shown as implemented as
respective methods, and also as a computer readable medium storing
instructions which upon execution causes the above noted features
to be operative.
While various aspects of the present disclosure have been described
above, it should be understood that they have been presented by way
of example only, and not limitation. Thus, the breadth and scope of
the present disclosure should not be limited by any of the
above-described embodiments, but should be defined only in
accordance with the following claims and their equivalents.
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